The Criss‐Cross Cycloaddition: A Simple Access to Valuable Heterocycles and Polymers

Abstract Aldazines are considered as the 2,3‐diaza analogs of 1,4‐disubstituted‐1,3‐butadienes, and the addition takes place at the 1,3‐ and 2,4‐positions instead of 1,4‐ or 1,2‐positions of the conjugated double bonds to furnish the two fused five‐membered heterocyclic rings, and hence due to this peculiar reactivity pattern, in 1917, the reaction was dubbed as the “criss‐cross” cycloaddition reaction by Bailey and co‐workers ‐ a special type of the [2+3]‐cycloaddition, or 1,3‐dipolar cycloaddition. Although, the reaction is known for more than a century, but still there are only countable reports available in the literature related to this wonderful cycloaddition reaction. Therefore, bearing the importance of this reaction in the generation of heterocyclic systems including polymeric materials in mind, we intended to comprehensively compile all the relevant data about this simple yet effective cycloaddition protocol. In this review article, we mainly categorized the whole document into four sections: intermolecular, intramolecular, combined inter‐intramolecular and polymerization reactions. We are in the opinion that this particular review article would provide a seed for future advancements ‐ cycloaddition in general and “criss‐cross cycloaddition” in particular, and one can foresee a bright future for this still young area of research.